Vapor generating apparatus



March 23, 1965 E. JOHNSON 3,174,464

VAPOR GENERATING APPARATUS Filed May 22, 1965 2 Sheets-Sheet 1 FIGJ 1653 P W A 1* 1 17 i A 36 E 37 :2 a! X & g 27 2e 25 Z 155 E 46 I 1 A gl gE -1 62 3; 2 I l a g g El 5, i g 44 22 -24 -1 fi 3 I i 32 f f iINVENTOR.

Lowell E. Johnson ATTORNEY March 23, 1965 E. JOHVNSON VAPOR GENERATINGAPPARATUS Filed May 22, 1965 2 Sheets-Sheet 2 FIG.3

lvllllllpllll INVENTOR. Lowell E. Johnson ATTORNEY United States Patent3,174,464 VAPOR GENERATHNG APPARATUS Lowell E. Eohnson, Alliance, Ohio,assignor to The Bahcoclr & Wilcox Company, New York, N.Y., a corporationof New Jersey Filed May 22, 1963, Ser. No. 282,331 4 Claims. (Cl.122-235) The present invention relates to the generation and heating ofvapor, and more particularly to vapor generating and heating unitswherein the heating gas temperature passing over fluid cooled heatexchange surfaces is reduced to acceptable values by the mixing of lowertemperature recirculated gases therewith.

In the art of steam generation and heating the use of recirculated gasesfor superheat temperature control and to temper or cool the combustiongases passing through the furnace and entering the convection heatinggas-pass is well known. The use of recirculated gases both for superheattemperature control and for gas tempering purposes has developed manyforms and modes of application specific to different configurations ofsteam generating and heating units. When recirculated gases are used fortempering purposes it is necessary to insure adequate mixing of the hotnewly formed combustion gases with the cooler recirculated gas so as toattain general temperature uniformity of the gas mixture leaving thefurnace and entering the steam heating banks. With an approximation ofgas temperature uniformity the quantity of recirculated gas flow can becontrolled to maintain the mixture at a maximum temperature foreffective steam heating while not exceeding safe metal temperatures inthe heating banks of the heater. Grdinarily, mixing of tempering gaswith newly generated combustion gas is attained by high velocityintroduction of the former gas into the latter so as to obtainpenetration.

In the present invention tempering gases are introduced into the upperportion of an upwardly elongated furnace directly beneath a nose ordeflecting baflle projecting into the furnace from one of the furnacewalls. Advantageously the fuel is introduced into the lower portion ofthe furnace through ports in a furnace wall opposite to the wallcontaining the nose or deflecting baflle. With this arrangement, thegaseous combustion products generated in the combustion of the fuel willtend to rise along the wall of the nose bafile and will flow along thelower surface of the batfle to accelerate in passing through the openingformed between the inner end of the nose baffle and the opposite wallcontaining the fuel admission ports. The tempering gas enters thefurnace at an angle to the flow of the combustion gases, and with thecombined flow occurring along the lower surface of the nose baffle andbeing accelerated to pass around the furnace end of the baflle, arethoroughly mixed so that the gas temperatures leaving the furnace aregenerally uniform. It has been found from model tests and actualexperience that intimate gas mixing is attained in the arrangement ofthe invention, with a minimum of excess tempering gas pressure requiredfor the introduction of the tempering gas into the furnace.

In many furnace constructions using a nose bafile for gas mixing andflow directing purposes the upwardly elongated furnace structure istransversely spaced from the associated vertically disposed convectiongas-pass, and the furnace gas outlet is connected with the convectiongas-pass inlet by a horizontally disposed gas-pass. The horizontalgas-pass is usually provided with conventional heat exchange surfaces,such as superheater and reheater tube banks. Advantageously, the spacebetween the furnace rear wall and the adjacent walls of the convectiongas-passes can be economically enclosed to provide a plenum chamber forthe tempering gas thereafter passed through spaced ports into thefurnace.

The various features of novelty which characterize my invention arepointed out with particularity in the claims annexed to and forming apart of this specification. For a better understanding of the inventionits operating advantages and specific objects attained by its use,reference should be had to the accompanying drawings and descriptivematter in which I have illustrated and described a preferred embodimentof the invention.

Of the drawings:

FIG. 1 is an elevation, partly in section, of a steam generating andheating unit incorporating the present invention;

FIG. 2 is an enlarged sectional elevation of a portion of the unit shownin FIG. 1;

FIG. 3 is a view of a portion of the structure as viewed from line 3-3of FIG. 2; and

FIG. 4 is a section taken on line 44 of FIG. 3.

In the drawings, the invention is illustrated as embodied in a highpressure, high capacity boiler of known type. As shown, an upwardlyelongated furnace 10 is provided with walls lined by fluid cooled tubes11, 12 and 13 where the tubes serve for the generation of steam. Thefurnace includes a hopper bottom 15 and a generally flat roof 16 withthe gas outlet 17 from the furnace positioned within the upper portion18 of the wall 21 containing the tubes 12. The gas outlet wall 21 may betermed the rear wall of the furnace for convenience. The opposite orfront wall 22 of the furnace containing the tubes 11 is provided in itslower portion with suitable openings 23 for the introduction ofcombustion constituents through, for example, oil burners 24. As shownin FIG. 1 the burners 24 are of the conventional type for theintroduction of fuel oil and combustion air, which is burned in thelower portion of the furnace.

As hereinafter described the rear wall 21 of the furnace 10 is providedwith a nose baffle 25 which projects inwardly of the furnace immediatelybelow the lower edge 26 of the gas outlet 17. The nose baflie ordinarilyextends into the furnace sufiiciently to direct the gas flow from thelower portion of the furnace toward the gas outlet 17 through an opening27 defined by the upright front wall 22 of the furnace and the tip 28 ofthe nose baflle 25. The flow area of the opening 27 usually represents50 to 70% of the total horizontal cross section area of the furnace 10.

The gases passing through the gas outlet 17 moves through a horizontallydisposed gas pass 30 opening into the upper portion of a downwardlyextending convection gas-pass 31 having a gas outlet 32 at the bottomthereof.

The gas flow through a vapor generating and heating unit of the typedisclosed is upwardly through the furnace 10 with the gases beingdeflected toward the front wall 22 by the nose baffle 25 with the gasesthereafter turning to move in a horizontal direction into the upperportion of the downpass 3-1. customarily, superheating and steamreheating surfaces 34 and 35 respectively, are provided above the uppersurface 33 of the nose baflle 25 and in the horizontal gas pass 30. Thegases in passing downwardly through the downpass flow over and aroundconvection heating surfaces which will include other steam reheatingsurfaces 36 and superheating surfaces 37 as well as economizer surfaces38. In the embodiment shown in FIG. 1 the downpass is provided with avertical row of tubes 40 to support the horizontally disposed banks ofheat exchange surfaces 36, 37 and 38 located in the downpass. Thesupport tubes tend to divide the pass into two interconnected gas flowpaths 41 and 42. The quantity of gases flowing through the parallel flowpaths 41 and 42 is regulated by suitable dampers 43 and 44 positionedbelow the economizer surfaces 38.

With the combustion gases produced in the furnace cooled by heatexchange in the generation of steam and in steam superheating andreheating surfaces, the gases will thereafter be passed through an airheater 45 on their way through a stack 46 for discharge to theatmosphere.

As shown in FIG. 1, the cooled combustion gases passing from theeconomizer 38 toward the air heater 45 serve as a source of supply forrecirculated gases discharged to the furnace for superheat temperaturecontrol purposes, and for tempering purposes. The recirculated gases arewithdrawn from the gas flow path through a duct 46 by a recirculatinggas fan 47 and discharged through a conduit 48 opening to the settingadjacent hopper bottom 15 of the furnace, and into a branch conduit 50which discharges into a plenum chamber 51 hereinafter described.

As shown in FIGS. 2, 3 and 4 the rear Wall 21 of the furnace is definedby a row of tangent tubes 12. It is, of course, understood that otherthan a tangent tube arrangement may be used to define the wall, such asfor example a row of tubes joined by metallic webs. The nose bafile 25shown in FIG. 2 is formed by bending a majority of the tubes such as 12Aof the rear wall 21 forwardly and upwardly to project into the furnace10. The tubes 12A are then reversely bent to define the nose 28 of thebaffle 25 with the tubes thereafter extended in an upwardly andoutwardly direction beyond the plane of the rear wall 21 and are thenbent upwardly along an extension of the plane of the adjacent wall 52 ofthe convection gas pass 31 (see FIG. 1) to discharge into a header 53for discharge to a drum 54 of the boiler. Other tubes of the rear wallsuch as tubes 12B extend upwardly across the base of the nose bafile 25,in the plane of the rear wall, and across the gas outlet 17 from thefurnace. These latter tubes are connected into the header 53 for thedischarge of the steam and water mixture therefrom into the drum 54. Thetubes 12B also serve as support tubes for the wall 21.

As shown, some of the tubes 12C of the rear wall 21 are bent outwardlyfrom the plane of the rear wall and then reversely bent to project in adirection parallel to the plane of the wall 21. Thereafter the tubes 120are bent toward the wall and into the plane of the wall. Thisconstruction is shown in FIGS. 2, 3 and 4, where three adjacent tubes12C of the rear wall are bent to form an opening or port 55 opening intothe furnace 10. In the embodiment shown, there are five ports 55 formedin the rear wall of the furnace, where each port is formed by displacingthree adjoining tubes outwardly of the wall.

The dimensions and the number of the port openings 55 formed in the rearwall 21 are selected in consideration of the expected amount of and thedesired velocity of the tempering gases to be introduced into thefurnace for gas temperature control purposes.

Advantageously, in a boiler of the type disclosed the space between therear wall 21 of the furnace 10 and the adjacent wall 52 of theconvection gas pass 31 is enclosed by a refractory floor 57 positioneddownwardly adjacent the lower edge of the gas inlet ports 55 and by sidewalls 58 enclosing the space between the bottom closure or floor 57, thewalls 21 and 52 and the rearward lower surface 60 of the horizontal gaspass. Such a closing structure defines a plenum chamber 51 which issupplied with tempering gases delivered thereto by a pair of conduits 50opening into the plenum chamber 51 through side wall inlet openings62formed in the side walls for the discharge of the desired quantitiesof tempering gas through the ports 55 into the furnace 10.

While the quantity of gases introduced into the furnace through theports 55 for gas tempering purposes will vary with differentinstallations, the usual range of tempering gas quantities will be from20 to 30% of the quantity of newly generated gases passed upwardlythrough the furnace at normal maximum fuel combustion rates. Thetempering gas quantity required for any particular installation isdependent upon a great number of factors, such as, the character of thefuel in use, the physical dimensions and configurations of the unit, themetallurgical character of heat exchange surfaces, and the like. Whenusing the arrangement of the present invention, the ports are spacedacross the rear wall of the furnace and are dimensioned to provide a gasvelocity entering the furnace of the order of 5000 to 10,000 feet perminute at the desired quantity.

While in accordance with the provisions of the statutes I haveillustrated and described herein the best form and mode of operation ofthe invention now known to me, those skilled in the art will understandthat changes may be made in the form of the apparatus disclosed withoutdeparting from the spirit of the invention covered by my claims, andthat certain features of my invention may sometimes be used to advantageWithout a corresponding use of other features.

What is claimed is:

1. In a boiler, the combination of upright walls defining an upwardlyelongated substantially unobstructed furnace, means defining a heatinggas outlet in the upper portion of one of the walls of said furnace, anose baffle projecting into said furnace from the wall of said heatinggas outlet and positioned downwardly adjacent the lower edge portion ofsaid outlet, means for introducing combustion constituents through thelower portion of a furnace wall opposite said gas outlet wall and at alevel beneath said nose bafile, the heating gases generated by thecombustion of said combustion constituents moving upwardly in the lowerportion of said furnace and being deflected toward the wall of saidcombustion constituent introduction by said nose battle, and means forintroducing tempering gas only through the wall of said gas outlet at alevel immediately below said nose baflle to intersect said heating gasesat an acute flow angle and to substantially uniformly mix therewith indischarging through said gas outlet.

2. In a boiler, the combination of upright walls defining an upwardlyelongated substantially unobstructed furnace, means for introducing afuel through one wall and into the lower portion of said furnace for thecombustion thereof and the generation of high temperature heating gasesthereby, means forming a heating gas outlet from the upper portion ofsaid furnace opposite said one wall, means forming an upright gas-passspaced from the wall of said furnace containing said gas outlet, ahorizontally disposed gas-pass connecting said furnace outlet with theupper portion of said upright gas-pass for flow of heating gas from saidfurnace through said horizontally disposed gas-pass and downwardly insaid upright gas-pass, means forming heat exchange surfaces in saidgas-passes, a nose bafile extending into said furnace beneath said gasoutlet to divert the heating gases toward said one wall of said furnaceand to thereafter pass in a generally horizontal direction through saidgas outlet, wall means positioned directly beneath the level of saidnose baffle to define a plenum chamber outwardly of said furnace, andmeans for recirculating cooled combustion gases to the furnace includingmeans for introducing said combustion gases from said plenum chamberthrough the outlet containing wall of the said furnace immediately belowsaid nose bafile to mix with combustion gases in the combined movementthereof around said nose baffle and through said outlet.

3. In a boiler, the combination of upright walls defining the front,rear and sides of an upwardly elongated substantially unobstructedfurnace, means for introducing a fuel through the front wall and intothe lower portion of said furnace for the combustion thereof and thegeneration of high temperature heating gases thereby, means forming aheating gas outlet from the upper rear wall portion of said furnace,walls defining an upright gas-pass spaced from the rear wall of saidfurnace, a horizontally disposed gas-pass connecting said furnace outletwith the upper portion of said upright gas-pass for flow of heating gasfrom said furnace through said horizontally disposed gas-pass anddownwardly in said upright gas-pass, means forming heat exchangesurfaces in said gas-passes to be traversed by the gases issuing fromsaid outlet, a nose bafile extending from side wall to side wall andinto said furnace from said rear wall beneath said gas outlet to divertthe heating gases toward the front wall of said furnace to thereafterpass in a generally horizontal direction through said gas outlet, wallmeans including a bottom wall beneath the level of said nose bafiieextending from the rear wall of said furnace to the adjacent wall ofsaid spaced gas-pass to define a plenum chamber between said furnace andsaid upright gas-pass, and means for recirculating cooled combustiongases to the furnace including means for introducing said recirculatedcombustion gases from said plenum chamber through the rear wall of thesaid furnace immediately below said nose baifie to mix with combustiongases in the combined movement thereof around said nose baflle andthrough said outlet.

4. In a boiler, the combination of upright walls defining the front,rear and sides of an upwardly elongated substantially unobstructedfurnace, means for introducing a fuel through the front wall and intothe lower portion of said furnace for the combustion thereof and thegeneration of high temperature heating gases thereby, means forming aheating gas outlet from the upper rear wall portion of said furnace,walls defining an upright gaspass spaced from the rear wall of saidfurnace, a horizontally disposed gasapass connecting said furnace outletwith the upper portion of said upright gas-pass for flow of heating gasfrom said furnace through said horizontally disposed gas-pass anddownwardly in said upright gaspass, means forming heat exchange surfacesin said gaspasses to be traversed by the gases issuing from said outlet,a nose bafile extending from side wall to side wall and into saidfurnace from said rear wall beneath said gas outlet to divert theheating gases toward the front wall of said furnace and to thereafterpass in a generally horizontal direction through said gas outlet, wallmeans including a bottom wall beneath the level of said nose bafileextending from the rear Wall of said furnace to the adjacent wall ofsaid spaced gas-pass to define a plenum chamber between said furnace andsaid upright gas-pass, and means for recirculating cooled combustiongases to the furnace from the lower portion of said upright gaspassincluding a horizontally spaced row of upwardly elongated inlet portsfor introducing said recirculated combustion gases from said plenumchamber through the rear wall of the said furnace immediately below saidnose baffle to mix with said heating gases in the combined movementthereof around said nose baffle and through said outlet.

References Cited in the file of this patent UNITED STATES PATENTS2,840,054 Rowand June 24, 1958 2,980,084 Koch et a1. Apr. 18, 19613,060,906 Rawdon Oct. 30, 1962 FOREIGN PATENTS 7 593,852 Canada Mar. 8,1960 OTHER REFERENCES Recirculated Gas, bulletin 6-96 by J. D. Andrews,Jr., et al., published by the Babcock and Wilcox Company, July 1959.

1. IN A BOILER, THE COMBINATION OF UPRIGHT WALLS DEFINING AN UPWARDLYELONGATED SUBSTANTIALLY UNOBSTRUCTED FURNACE, MEANS DEFINING A HEATINGGAS OUTLET IN THE UPPER PORTION OF ONE OF THE WALLS OF SAID FURNACE, ANOSE BAFFLE PROJECTING INTO SAID FURNACE FROM THE WALL OF SAID HEATINGGAS OUTLET AND POSITIONED DOWNWARDLY ADJACENT THE LOWER EDGE PORTION OFSAID OUTLET, MEANS FOR INTRODUCING COMBUSTION CONSTITUENTS THROUGH THELOWER PORTION OF A FURNACE WALL OPPOSITE SAID GAS OUTLET WALL AND AT ALEVEL BENEATH SAID NOSE BAFFLE, THE HEATING GASES GENERATED BY THECOMBUSTION OF SAID COMBUSTION CONSTITUENTS MOVING UPWARDLY IN THE LOWERPORTION OF SAID FURNACE AND BEING DEFLECTED TOWARD THE WALL PORTION OFSAID FURNACE AND BEING INTRODUTION BY SAID NOSE BAFFLE, AND MEANS FORINTRODUCING TEMPERING GAS ONLY THROUGH THE WALL OF SAID GAS OUTLET AT ALEVEL IMMEDIATELY BELOW SAID BOSE BAFFLE TO INTERSECT SAID HEATING GASESAT AN ACUTE FLOW ANGLE AND TO SUBSTANTIALLY UNIFORMLY MIX THEREWITH INDISCHARGING THROUGH SAID GAS OUTLET.